P1288: ALTERED AMINO ACID HOMEOSTASIS CAN ELICIT AN ADAPTIVE RESPONSE VIA UPREGULATION OF UFMYLATION IN HODGKIN LYMPHOMA
Authors: A. Romano, G. Scandura, D. Tibullo, A. M. Amorini, E. La Spina, A. Barbato, C. Giallongo, C. Cerchione, G. Simonetti, G. Martinelli, F. Di Raimondo
Journal: HemaSphere (2022)

Background: Our previous work showed that Arginase (ARG-1) and Indoleamine Deoxigenase (IDO-1) are increased in tumour microenvironment of classic Hodgkin Lymphoma (HL), but the consequences of arginine (arg) and tryptophan (trp) deprivation on neoplastic cells fitness are largely unknown. Aims: To identify the adaptive response to arg and trp deprivation at metabolic and transcriptional level in HL. Methods: In three human HL cell lines (L428, L540 and KM-H2) individually cultured with customized complete media or deprived of arg/trp, we performed an integrative metabolic and transcriptome profiling, respectively by Metabolon Inc and Illumina RNA-seq platforms. Findings about the amino acid metabolism were validated in both lymph-node and peripheral blood of 64 consecutive newly-diagnosed patients affected by advanced stage HL. Results: In vitro, specific-amino acid deficiency leads to an increase in uptake of free fatty acids from the media to maintain membrane integrity. Consistent with a metabolic rewiring to maintain mitochondrial integrity (the pyruvate is an important intermediary in the conversion of carbohydrates into fatty acids), the adaptive response to arg deprivation was associated to increased oxidative stress (reduced glutathione, depletion of gamma-glutamylcysteine, increased cystine, the oxidative product of cysteine, and methionine sulfoxide (an oxidation product of methionine), while no significant changes were observed in trp deprivation. Gene set enrichment analysis (GSEA) showed deep transcriptome rearrangements in KMH2 and HDMYZ cell lines upon arg deprivation, involving upregulation of genes required for the unfolded protein response p53 pathway and networks and proteosome degradation, with a minimal effect on metabolism features, except the upregulation of genes involved in lactate generation and degradation. Upon both arg and trp deprivation, all cell lines tested showed down-regulation of CCNI2, LCROL, MKI67, NCAPG, PEX10 and UFSP2, confirmed by increased ribosome stalling. Thus, we disclosed how amino acid starvation engages the UFMylation pathway, an adaptive response never investigated before in HL. Despite ARG-1 and IDO-1 cells were significantly enriched in HL tissue samples as compared with control reactive lymph node samples, peripheral blood HL patients showed dysregulated distribution of aminoacids, with significant increase of arginine, tryptophan, kynurenine, glutamate (specular to reduced amounts in the lymph node) and reduction of glutamine, asparagine, histidine, threonine, alanine, valine and methionine, confirming in vivo the relevance of amino acid deprivation in HL. Summary/Conclusion: In HL there is a dysregulation in amino acid metabolism as consequence of the complex crosstalk between neoplastic cells and their microenvironment. However, compensatory pathways can be elicited to maintain arginine and tryptophan availability in peripheral blood, where several amino acids, other than arginine and tryptophan, are reduced. Further studies are required to unveil the adaptive response to amino acid deprivation in HL.